The greeting is now always read manually,
even for STARTTLS connections,
so the errors returned on failure to read form the stream
are the same regardless of the connection type.
This change introduces new config options
`proxy_enabled` and `proxy_url`
that replace `socks5_*`.
Tested with deltachat-repl
by starting it with
`cargo run --locked -p deltachat-repl -- deltachat-db` and running
```
> set proxy_enabled 1
> set proxy_url ss://...
> setqr dcaccount:https://chatmail.example.org/new
> configure
```
Previously for each connection candidate (essentially host and port
pair) after resolving the host to a list of IPs Delta Chat iterated IP
addresses one by one. Now for IMAP and SMTP we try up to 5 IP addresses
in parallel. We start with one connection and add more connections
later. If some connection fails, e.g. we try to connect to IPv6 on IPv4
network and get "Network is unreachable" (ENETUNREACH) error, we replace
failed connection with another one immediately.
Co-authored-by: Hocuri <hocuri@gmx.de>
Apparently some providers fail TLS connection
with "no_application_protocol" alert
even when requesting "imap" protocol for IMAP connection
and "smtp" protocol for SMTP connection.
Fixes <https://github.com/deltachat/deltachat-core-rust/issues/5892>.
Single function smtp::connect::connect_stream
returns a stream of a single `dyn` type
that can be a TLS, STARTTLS or plaintext
connection established over SOCKS5 or directly.
